High Quality Content by WIKIPEDIA articles! In the strict sense of the term, metasyntactic variable, in computer science, is a placeholder name or an alias term commonly used to denote an arbitrary thing, or an arbitrary member of a class of things under discussion, i.e. a metavariable. The word foo as used in IETF RFCs is a good example. By mathematical analogy, a metasyntactic variable is a word that is a variable for other words, just as in algebra letters are used as variables for numbers. Any symbol or word which does not violate the syntactic rules of the language can be used as a metasyntactic variable. For specifications written in natural language, nonsense words are commonly used as metasyntactic variables.